Organic electroluminescent materials and devices

ABSTRACT

A novel type of blue emitter is described based on the azaphenanthridine imidazole ligand. The preferred use of this moiety for generating blue phosphorescence is as part of a symmetric platinum tetradentate complex.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. Nos. 61/979,103, filed Apr. 14, 2014, and 61/991,720,filed May 12, 2014, the entire contents of each of which is incorporatedherein by reference.

PARTIES TO A JOINT RESEARCH AGREEMENT

The claimed invention was made by, on behalf of, and/or in connectionwith one or more of the following parties to a joint universitycorporation research agreement: Regents of the University of Michigan,Princeton University, University of Southern California, and theUniversal Display Corporation. The agreement was in effect on and beforethe date the claimed invention was made, and the claimed invention wasmade as a result of activities undertaken within the scope of theagreement.

FIELD OF THE INVENTION

The present invention relates to compounds for use as emitters anddevices, such as organic light emitting diodes, including the same.

BACKGROUND

Opto-electronic devices that make use of organic materials are becomingincreasingly desirable for a number of reasons. Many of the materialsused to make such devices are relatively inexpensive, so organicopto-electronic devices have the potential for cost advantages overinorganic devices. In addition, the inherent properties of organicmaterials, such as their flexibility, may make them well suited forparticular applications such as fabrication on a flexible substrate.Examples of organic opto-electronic devices include organic lightemitting devices (OLEDs), organic phototransistors, organic photovoltaiccells, and organic photodetectors. For OLEDs, the organic materials mayhave performance advantages over conventional materials. For example,the wavelength at which an organic emissive layer emits light maygenerally be readily tuned with appropriate dopants.

OLEDs make use of thin organic films that emit light when voltage isapplied across the device. OLEDs are becoming an increasinglyinteresting technology for use in applications such as flat paneldisplays, illumination, and backlighting. Several OLED materials andconfigurations are described in U.S. Pat. Nos. 5,844,363, 6,303,238, and5,707,745, which are incorporated herein by reference in their entirety.

One application for phosphorescent emissive molecules is a full colordisplay. Industry standards for such a display call for pixels adaptedto emit particular colors, referred to as “saturated” colors. Inparticular, these standards call for saturated red, green, and bluepixels. Color may be measured using CIE coordinates, which are wellknown to the art.

One example of a green emissive molecule is tris(2-phenylpyridine)iridium, denoted Ir(ppy)3, which has the following structure:

In this, and later figures herein, we depict the dative bond fromnitrogen to metal (here, Ir) as a straight line.

As used herein, the term “organic” includes polymeric materials as wellas small molecule organic materials that may be used to fabricateorganic opto-electronic devices. “Small molecule” refers to any organicmaterial that is not a polymer, and “small molecules” may actually bequite large. Small molecules may include repeat units in somecircumstances. For example, using a long chain alkyl group as asubstituent does not remove a molecule from the “small molecule” class.Small molecules may also be incorporated into polymers, for example as apendent group on a polymer backbone or as a part of the backbone. Smallmolecules may also serve as the core moiety of a dendrimer, whichconsists of a series of chemical shells built on the core moiety. Thecore moiety of a dendrimer may be a fluorescent or phosphorescent smallmolecule emitter. A dendrimer may be a “small molecule,” and it isbelieved that all dendrimers currently used in the field of OLEDs aresmall molecules.

As used herein, “top” means furthest away from the substrate, while“bottom” means closest to the substrate. Where a first layer isdescribed as “disposed over” a second layer, the first layer is disposedfurther away from substrate. There may be other layers between the firstand second layer, unless it is specified that the first layer is “incontact with” the second layer. For example, a cathode may be describedas “disposed over” an anode, even though there are various organiclayers in between.

As used herein, “solution processible” means capable of being dissolved,dispersed, or transported in and/or deposited from a liquid medium,either in solution or suspension form.

A ligand may be referred to as “photoactive” when it is believed thatthe ligand directly contributes to the photoactive properties of anemissive material. A ligand may be referred to as “ancillary” when it isbelieved that the ligand does not contribute to the photoactiveproperties of an emissive material, although an ancillary ligand mayalter the properties of a photoactive ligand.

As used herein, and as would be generally understood by one skilled inthe art, a first “Highest Occupied Molecular Orbital” (HOMO) or “LowestUnoccupied Molecular Orbital” (LUMO) energy level is “greater than” or“higher than” a second HOMO or LUMO energy level if the first energylevel is closer to the vacuum energy level. Since ionization potentials(IP) are measured as a negative energy relative to a vacuum level, ahigher HOMO energy level corresponds to an IP having a smaller absolutevalue (an IP that is less negative). Similarly, a higher LUMO energylevel corresponds to an electron affinity (EA) having a smaller absolutevalue (an EA that is less negative). On a conventional energy leveldiagram, with the vacuum level at the top, the LUMO energy level of amaterial is higher than the HOMO energy level of the same material. A“higher” HOMO or LUMO energy level appears closer to the top of such adiagram than a “lower” HOMO or LUMO energy level.

used herein, and as would be generally understood by one skilled in theart, a first work function is “greater than” or “higher than” a secondwork function if the first work function has a higher absolute value.Because work functions are generally measured as negative numbersrelative to vacuum level, this means that a “higher” work function ismore negative. On a conventional energy level diagram, with the vacuumlevel at the top, a “higher” work function is illustrated as furtheraway from the vacuum level in the downward direction. Thus, thedefinitions of HOMO and LUMO energy levels follow a different conventionthan work functions.

More details on OLEDs, and the definitions described above, can be foundin U.S. Pat. No. 7,279,704, which is incorporated herein by reference inits entirety.

In some bis-bidentate and symmetric tetradentate imidazolephenanthridine platinum complexes, the emission energy is not blueenough for display and lighting applications. Furthermore, theuncoordinated nitrogen in the phenanthridine ring system presents astability issue as it may be susceptible to protonation in the excitedstate. There is a need in the art for novel compounds with strongblue-shifting effects that are not susceptible to protonation of theuncoordinated nitrogen. The present invention addresses this unmet need.

SUMMARY OF THE INVENTION

According to an embodiment, a compound is provided having the formula:

wherein A and B are independently selected from the group consisting ofa 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein one of A and B is an anionic coordinating atom, and the other ofA and B is a neutral coordinating atoms;

wherein X and Y are independently selected from the group consisting ofBR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, alkyl, aryl, SiR′R″, andGeR′R″;

wherein at least one of X and Y is present;

wherein M is Pt or Pd;

wherein R^(l) and R³ each independently represent mono, ordi-substitution, or no substitution;

wherein R² represent mono, di, tri, or tetra-substitution, or nosubstitution;

wherein R¹, R², R³, R′, and R″ are each independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any adjacent R¹, R², R³, R′, and R″ are optionally joined toform a ring.

In one embodiment, M is Pt.

In one embodiment, the compound has the formula:

In one embodiment, the compound has the formula:

wherein R is selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one embodiment, R is selected from the group consisting of alkyl,cycloalkyl, silyl, aryl, heteroaryl, and combinations thereof. Inanother embodiment, R is selected from the group consisting of methyl,ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl,pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl,1,2-dimethylpropyl, 2,2-dimethylpropyl, cyclopentyl, cyclohexyl, phenyl,2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 2,6-diisopropylphenyl, andcombinations thereof.

In one embodiment, only one of X and Y is present.

In one embodiment, the compound is selected from the group consistingof:

wherein R⁶ represents mono, di, tri, or tetra-substitution, or nosubstitution;

wherein R⁴, R⁵, and R⁶ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any adjacent R⁴, R⁵, and R⁶ are optionally joined to form aring.

In one embodiment. A-B is selected from the groun consisting of:

wherein each X¹ to X¹³ are independently selected from the groupconsisting of carbon and nitrogen;

wherein X is selected from the group consisting of BR′, NR′, PR′, O, S,Se, C═O, S═O, SO₂, CR′R″, SiR′R″, and GeR′R″;

wherein R′ and R″ are optionally fused or joined to form a ring;

wherein each R_(a), R_(b), R_(c), and R_(d) may represent from monosubstitution to the possible maximum number of substitution, or nosubstitution;

wherein R_(L) represents mono substitution, or no substitution;

wherein R_(a), R_(b), R_(c), R_(d) and R_(L) are each independentlyselected from the group consisting of hydrogen, deuterium, halide,alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino,silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,acyl, carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein when R_(a), R_(b), R_(c), and R_(d) represent at least disubstitution, each of the two adjacent R_(a), two adjacent R_(b), twoadjacent R_(c), and two adjacent R_(d) are optionally fused or joined toform a ring;

wherein R_(L), is optionally a linker to function as X or Y; and

wherein when X¹ to X¹³ are used to link to X or Y, that X¹ to X¹³ iscarbon.

In one embodiment, the compound is selected from the group consistingof:

According to another embodiment, a first device comprising a firstorganic light emitting device is also provided. The first organic lightemitting device can include an anode, a cathode, and an organic layer,disposed between the anode and the cathode. The organic layer caninclude a compound of Formula I. The first device can be a consumerproduct, an organic light-emitting device, and/or a lighting panel.

In one embodiment, the first device comprises a first organic lightemitting device, the first organic light emitting device comprising:

an anode;

a cathode; and

an organic layer, disposed between the anode and the cathode, comprisinga compound having the formula:

wherein A and B are independently selected from the group consisting ofa 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein one of A and B is an anionic coordinating atom, and the other ofA and B is a neutral coordinating atoms;

wherein X and Y are independently selected from the group consisting ofBR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, alkyl, aryl, SiR′R″, andGeR′R″;

wherein at least one of X and Y is present;

wherein M is Pt or Pd;

wherein R^(l) and R³ each independently represent mono, ordi-substitution, or no substitution;

wherein R² represent mono, di, tri, or tetra-substitution, or nosubstitution;

wherein R¹, R², R³, R′, and R″ are each independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any adjacent R¹, R², R³, R′, and R″ are optionally joined toform a ring.

In one embodiment, the first device is selected from the groupconsisting of a consumer product, an electronic component module, anorganic light-emitting device, and a lighting panel. In anotherembodiment, the organic layer is an emissive layer and the compound isan emissive dopant or a non-emissive dopant. In another embodiment, theorganic layer is a charge transporting layer and the compound is acharge transporting material in the organic layer. In anotherembodiment, the organic layer is a blocking layer and the compound is ablocking material in the organic layer.

In one embodiment, the organic layer further comprises a host; whereinthe host comprises a triphenylene containing benzo-fused thiophene orbenzo-fused furan;

wherein any substituent in the host is an unfused substituentindependently selected from the group consisting of C_(n)H_(2n+1),OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂, N(Ar₂)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1), Ar₁, Ar₁-Ar₂, C_(n)H_(2n)-Ar₁, orno substitution;

wherein n is from 1 to 10; and

wherein Ar₁ and Ar₂ are independently selected from the group consistingof benzene, biphenyl, naphthalene, triphenylene, carbazole, andheteroaromatic analogs thereof.

In one embodiment, the organic layer further comprises a host, whereinthe host comprises at least one chemical group selected from the groupconsisting of triphenylene, carbazole, dibenzothiphene, dibenzofuran,dibenzoselenophene, azatriphenylene, azacarbazole, aza-dibenzothiophene,aza-dibenzofuran, and aza-dibenzoselenophene.

In one embodiment, the organic layer further comprises a host and thehost is selected from the group consisting of:

and combinations thereof.

In one embodiment, the organic layer further comprises a host and thehost comprises a metal complex.

According to another embodiment, a formulation comprising the abovecompound is also provided. In one embodiment, the formulation comprisesa compound having the formula:

wherein A and B are independently selected from the group consisting ofa 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein one of A and B is an anionic coordinating atom, and the other ofA and B is a neutral coordinating atoms;

wherein X and Y are independently selected from the group consisting ofBR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, alkyl, aryl, SiR′R″, andGeR′R″;

wherein at least one of X and Y is present;

wherein M is Pt or Pd;

wherein R^(l) and R³ each independently represent mono, ordi-substitution, or no substitution;

wherein R² represent mono, di, tri, or tetra-substitution, or nosubstitution;

wherein R¹, R², R³, R′, and R″ are each independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any adjacent R¹, R², R³, R′, and R″ are optionally joined toform a ring.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an organic light emitting device.

FIG. 2 shows an inverted organic light emitting device that does nothave a separate electron transport layer.

FIG. 3 shows an emission spectrum of Comparative Example 1 measured at77K in 2-methyltetrahydrofuran solvent.

FIG. 4 shows an emission spectra of Comparative Example 2 in solid statePMMA matrix and 77K and Room Temperature 2-methyltetrahydrofuransolvent.

FIG. 5 shows an emission spectra of Comparative Example 3 in 77K andRoom Temperature 2-methyltetrahydrofuran solvent.

FIG. 6 shows spectral data for Comparative Example 5 in 77K2-methyltetrahydrofuran solvent.

DETAILED DESCRIPTION

Generally, an OLED comprises at least one organic layer disposed betweenand electrically connected to an anode and a cathode. When a current isapplied, the anode injects holes and the cathode injects electrons intothe organic layer(s). The injected holes and electrons each migratetoward the oppositely charged electrode. When an electron and holelocalize on the same molecule, an “exciton,” which is a localizedelectron-hole pair having an excited energy state, is formed. Light isemitted when the exciton relaxes via a photoemissive mechanism. In somecases, the exciton may be localized on an excimer or an exciplex.Non-radiative mechanisms, such as thermal relaxation, may also occur,but are generally considered undesirable.

The initial OLEDs used emissive molecules that emitted light from theirsinglet states (“fluorescence”) as disclosed, for example, in U.S. Pat.No. 4,769,292, which is incorporated by reference in its entirety.Fluorescent emission generally occurs in a time frame of less than 10nanoseconds.

More recently, OLEDs having emissive materials that emit light fromtriplet states (“phosphorescence”) have been demonstrated. Baldo et al.,“Highly Efficient Phosphorescent Emission from OrganicElectroluminescent Devices,” Nature, vol. 395, 151-154, 1998;(“Baldo-I”) and Baldo et al., “Very high-efficiency green organiclight-emitting devices based on electrophosphorescence,” Appl. Phys.Lett., vol. 75, No. 3, 4-6 (1999) (“Baldo-II”), which are incorporatedby reference in their entireties. Phosphorescence is described in moredetail in U.S. Pat. No. 7,279,704 which is incorporated by reference inits entirety.

FIG. 1 shows an organic light emitting device 100. The figures are notnecessarily drawn to scale. Device 100 may include a substrate 110, ananode 115, a hole injection layer 120, a hole transport layer 125, anelectron blocking layer 130, an emissive layer 135, a hole blockinglayer 140, an electron transport layer 145, an electron injection layer150, a protective layer 155, a cathode 160, and a barrier layer 170.Cathode 160 is a compound cathode having a first conductive layer 162and a second conductive layer 164. Device 100 may be fabricated bydepositing the layers described, in order. The properties and functionsof these various layers, as well as example materials, are described inmore detail in U.S. Pat. No. 7,279,704 which is incorporated byreference in its entirety.

More examples for each of these layers are available. For example, aflexible and transparent substrate-anode combination is disclosed inU.S. Pat. No. 5,844,363, which is incorporated by reference in itsentirety. An example of a p-doped hole transport layer is m-MTDATA dopedwith F₄-TCNQ at a molar ratio of 50:1, as disclosed in U.S. PatentApplication Publication No. 2003/0230980, which is incorporated byreference in its entirety. Examples of emissive and host materials aredisclosed in U.S. Pat. No. 6,303,238 to Thompson et al., which isincorporated by reference in its entirety. An example of an n-dopedelectron transport layer is BPhen doped with Li at a molar ratio of 1:1,as disclosed in U.S. Patent Application Publication No. 2003/0230980,which is incorporated by reference in its entirety. U.S. Pat. Nos.5,703,436 and 5,707,745, which are incorporated by reference in theirentireties, disclose examples of cathodes including compound cathodeshaving a thin layer of metal such as Mg:Ag with an overlyingtransparent, electrically-conductive, sputter-deposited ITO layer. Thetheory and use of blocking layers is described in more detail in U.S.Pat. No. 6,097,147 and U.S. Patent Application Publication No.2003/0230980, which are incorporated by reference in their entireties.Examples of injection layers are provided in U.S. Patent ApplicationPublication No. 2004/0174116, which is incorporated by reference in itsentirety. A description of protective layers may be found in U.S. PatentApplication Publication No. 2004/0174116, which is incorporated byreference in its entirety.

FIG. 2 shows an inverted OLED 200. The device includes a substrate 210,a cathode 215, an emissive layer 220, a hole transport layer 225, and ananode 230. Device 200 may be fabricated by depositing the layersdescribed, in order. Because the most common OLED configuration has acathode disposed over the anode, and device 200 has cathode 215 disposedunder anode 230, device 200 may be referred to as an “inverted” OLED.Materials similar to those described with respect to device 100 may beused in the corresponding layers of device 200. FIG. 2 provides oneexample of how some layers may be omitted from the structure of device100.

The simple layered structure illustrated in FIGS. 1 and 2 is provided byway of non-limiting example, and it is understood that embodiments ofthe invention may be used in connection with a wide variety of otherstructures. The specific materials and structures described areexemplary in nature, and other materials and structures may be used.Functional OLEDs may be achieved by combining the various layersdescribed in different ways, or layers may be omitted entirely, based ondesign, performance, and cost factors. Other layers not specificallydescribed may also be included. Materials other than those specificallydescribed may be used. Although many of the examples provided hereindescribe various layers as comprising a single material, it isunderstood that combinations of materials, such as a mixture of host anddopant, or more generally a mixture, may be used. Also, the layers mayhave various sublayers. The names given to the various layers herein arenot intended to be strictly limiting. For example, in device 200, holetransport layer 225 transports holes and injects holes into emissivelayer 220, and may be described as a hole transport layer or a holeinjection layer. In one embodiment, an OLED may be described as havingan “organic layer” disposed between a cathode and an anode. This organiclayer may comprise a single layer, or may further comprise multiplelayers of different organic materials as described, for example, withrespect to FIGS. 1 and 2.

Structures and materials not specifically described may also be used,such as OLEDs comprised of polymeric materials (PLEDs) such as disclosedin U.S. Pat. No. 5,247,190 to Friend et al., which is incorporated byreference in its entirety. By way of further example, OLEDs having asingle organic layer may be used. OLEDs may be stacked, for example asdescribed in U.S. Pat. No. 5,707,745 to Forrest et al, which isincorporated by reference in its entirety. The OLED structure maydeviate from the simple layered structure illustrated in FIGS. 1 and 2.For example, the substrate may include an angled reflective surface toimprove out-coupling, such as a mesa structure as described in U.S. Pat.No. 6,091,195 to Forrest et al., and/or a pit structure as described inU.S. Pat. No. 5,834,893 to Bulovic et al., which are incorporated byreference in their entireties.

Unless otherwise specified, any of the layers of the various embodimentsmay be deposited by any suitable method. For the organic layers,preferred methods include thermal evaporation, ink-jet, such asdescribed in U.S. Pat. Nos. 6,013,982 and 6,087,196, which areincorporated by reference in their entireties, organic vapor phasedeposition (OVPD), such as described in U.S. Pat. No. 6,337,102 toForrest et al., which is incorporated by reference in its entirety, anddeposition by organic vapor jet printing (OVJP), such as described inU.S. Pat. No. 7,431,968, which is incorporated by reference in itsentirety. Other suitable deposition methods include spin coating andother solution based processes. Solution based processes are preferablycarried out in nitrogen or an inert atmosphere. For the other layers,preferred methods include thermal evaporation. Preferred patterningmethods include deposition through a mask, cold welding such asdescribed in U.S. Pat. Nos. 6,294,398 and 6,468,819, which areincorporated by reference in their entireties, and patterning associatedwith some of the deposition methods such as ink jet and OVJD. Othermethods may also be used. The materials to be deposited may be modifiedto make them compatible with a particular deposition method. Forexample, substituents such as alkyl and aryl groups, branched orunbranched, and preferably containing at least 3 carbons, may be used insmall molecules to enhance their ability to undergo solution processing.Substituents having 20 carbons or more may be used, and 3-20 carbons isa preferred range. Materials with asymmetric structures may have bettersolution processibility than those having symmetric structures, becauseasymmetric materials may have a lower tendency to recrystallize.Dendrimer substituents may be used to enhance the ability of smallmolecules to undergo solution processing.

Devices fabricated in accordance with embodiments of the presentinvention may further optionally comprise a barrier layer. One purposeof the barrier layer is to protect the electrodes and organic layersfrom damaging exposure to harmful species in the environment includingmoisture, vapor and/or gases, etc. The barrier layer may be depositedover, under or next to a substrate, an electrode, or over any otherparts of a device including an edge. The barrier layer may comprise asingle layer, or multiple layers. The barrier layer may be formed byvarious known chemical vapor deposition techniques and may includecompositions having a single phase as well as compositions havingmultiple phases. Any suitable material or combination of materials maybe used for the barrier layer. The barrier layer may incorporate aninorganic or an organic compound or both. The preferred barrier layercomprises a mixture of a polymeric material and a non-polymeric materialas described in U.S. Pat. No. 7,968,146, PCT Pat. Application Nos.PCT/US2007/023098 and PCT/US2009/042829, which are herein incorporatedby reference in their entireties. To be considered a “mixture”, theaforesaid polymeric and non-polymeric materials comprising the barrierlayer should be deposited under the same reaction conditions and/or atthe same time. The weight ratio of polymeric to non-polymeric materialmay be in the range of 95:5 to 5:95. The polymeric material and thenon-polymeric material may be created from the same precursor material.In one example, the mixture of a polymeric material and a non-polymericmaterial consists essentially of polymeric silicon and inorganicsilicon.

Devices fabricated in accordance with embodiments of the invention canbe incorporated into a wide variety of electronic component modules (orunits) that can be incorporated into a variety of electronic products orintermediate components. Examples of such electronic products orintermediate components include display screens, lighting devices suchas discrete light source devices or lighting panels, etc. that can beutilized by the end-user product manufacturers. Such electroniccomponent modules can optionally include the driving electronics and/orpower source(s). Devices fabricated in accordance with embodiments ofthe invention can be incorporated into a wide variety of consumerproducts that have one or more of the electronic component modules (orunits) incorporated therein. Such consumer products would include anykind of products that include one or more light source(s) and/or one ormore of some type of visual displays. Some examples of such consumerproducts include flat panel displays, computer monitors, medicalmonitors, televisions, billboards, lights for interior or exteriorillumination and/or signaling, heads-up displays, fully or partiallytransparent displays, flexible displays, laser printers, telephones,cell phones, tablets, phablets, personal digital assistants (PDAs),laptop computers, digital cameras, camcorders, viewfinders,micro-displays, 3-D displays, vehicles, a large area wall, theater orstadium screen, or a sign. Various control mechanisms may be used tocontrol devices fabricated in accordance with the present invention,including passive matrix and active matrix. Many of the devices areintended for use in a temperature range comfortable to humans, such as18 degrees C. to 30 degrees C., and more preferably at room temperature(20-25 degrees C.), but could be used outside this temperature range,for example, from −40 degree C. to +80 degree C.

The materials and structures described herein may have applications indevices other than OLEDs. For example, other optoelectronic devices suchas organic solar cells and organic photodetectors may employ thematerials and structures. More generally, organic devices, such asorganic transistors, may employ the materials and structures.

The term “halo,” “halogen,” or “halide” as used herein includesfluorine, chlorine, bromine, and iodine.

The term “alkyl” as used herein contemplates both straight and branchedchain alkyl radicals. Preferred alkyl groups are those containing fromone to fifteen carbon atoms and includes methyl, ethyl, propyl,isopropyl, butyl, isobutyl, tert-butyl, and the like. Additionally, thealkyl group may be optionally substituted.

The term “cycloalkyl” as used herein contemplates cyclic alkyl radicals.Preferred cycloalkyl groups are those containing 3 to 7 carbon atoms andincludes cyclopropyl, cyclopentyl, cyclohexyl, and the like.Additionally, the cycloalkyl group may be optionally substituted.

The term “alkenyl” as used herein contemplates both straight andbranched chain alkene radicals. Preferred alkenyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkenyl groupmay be optionally substituted.

The term “alkynyl” as used herein contemplates both straight andbranched chain alkyne radicals. Preferred alkynyl groups are thosecontaining two to fifteen carbon atoms. Additionally, the alkynyl groupmay be optionally substituted.

The terms “aralkyl” or “arylalkyl” as used herein are usedinterchangeably and contemplate an alkyl group that has as a substituentan aromatic group. Additionally, the aralkyl group may be optionallysubstituted.

The term “heterocyclic group” as used herein contemplates aromatic andnon-aromatic cyclic radicals. Hetero-aromatic cyclic radicals also meansheteroaryl. Preferred hetero-non-aromatic cyclic groups are thosecontaining 3 or 7 ring atoms which includes at least one hetero atom,and includes cyclic amines such as morpholino, piperdino, pyrrolidino,and the like, and cyclic ethers, such as tetrahydrofuran,tetrahydropyran, and the like. Additionally, the heterocyclic group maybe optionally substituted.

The term “aryl” or “aromatic group” as used herein contemplatessingle-ring groups and polycyclic ring systems. The polycyclic rings mayhave two or more rings in which two carbons are common to two adjoiningrings (the rings are “fused”) wherein at least one of the rings isaromatic, e.g., the other rings can be cycloalkyls, cycloalkenyls, aryl,heterocycles, and/or heteroaryls. Additionally, the aryl group may beoptionally substituted.

The term “heteroaryl” as used herein contemplates single-ringhetero-aromatic groups that may include from one to three heteroatoms,for example, pyrrole, furan, thiophene, imidazole, oxazole, thiazole,triazole, pyrazole, pyridine, pyrazine and pyrimidine, and the like. Theterm heteroaryl also includes polycyclic hetero-aromatic systems havingtwo or more rings in which two atoms are common to two adjoining rings(the rings are “fused”) wherein at least one of the rings is aheteroaryl, e.g., the other rings can be cycloalkyls, cycloalkenyls,aryl, heterocycles, and/or heteroaryls. Additionally, the heteroarylgroup may be optionally substituted.

The alkyl, cycloalkyl, alkenyl, alkynyl, aralkyl, heterocyclic group,aryl, and heteroaryl may be optionally substituted with one or moresubstituents selected from the group consisting of hydrogen, deuterium,halogen, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, cyclic amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl,alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylic acid, ether,ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, andcombinations thereof.

As used herein, “substituted” indicates that a substituent other than His bonded to the relevant position, such as carbon. Thus, for example,where R^(l) is mono-substituted, then one R¹ must be other than H.Similarly, where R^(l) is di-substituted, then two of R^(l) must beother than H. Similarly, where R^(l) is unsubstituted, R^(l) is hydrogenfor all available positions.

The “aza” designation in the fragments described herein, i.e.aza-dibenzofuran, aza-dibenzothiophene, etc. means that one or more ofthe C—H groups in the respective fragment can be replaced by a nitrogenatom, for example, and without any limitation, azatriphenyleneencompasses both dibenzo[fh]quinoxaline and dibenzo[fh]quinoline. One ofordinary skill in the art can readily envision other nitrogen analogs ofthe aza-derivatives described above, and all such analogs are intendedto be encompassed by the terms as set forth herein.

It is to be understood that when a molecular fragment is described asbeing a substituent or otherwise attached to another moiety, its namemay be written as if it were a fragment (e.g. phenyl, phenylene,naphthyl, dibenzofuryl) or as if it were the whole molecule (e.g.benzene, naphthalene, dibenzofuran). As used herein, these differentways of designating a substituent or attached fragment are considered tobe equivalent.

In comparison to bidentate ligands, tetradentate complexes aredemonstrated to have superior emissive properties. Although not wishingto be bound by any particular theory, this effect is believed to be dueto a distortion of the square planar geometry in the excited state thatleads to non-radiative decay. It is hypothesized that the tetradentateconfiguration inhibits this distortion, resulting in improved emissiveproperties when compared to an analogous bis-bidentate structure. Insome bis-bidentate and symmetric tetradentate imidazole phenanthridineplatinum complexes, the emission energy is not blue enough for displayand lighting applications. Therefore, the present invention is based inpart on the discovery that substituting nitrogen in the imidazolephenanthridine ring system to form an azaphenanthridine imidazole ligandprovides a strong blue-shifting effect not observed in the imidazolephenanthridine ring system.

Substitution of nitrogen in a specific position in the polycyclicazaphenanthridine imidazole ligand system can lead to a profound blueshifting effect. However, the uncoordinated nitrogen presents astability issue as it may be susceptible to protonation in the excitedstate. The three ring structure of azaphenanthridine imidazole has asite that, when substituted with a bulky group, such as an aryl ring,shields the uncoordinated nitrogen from the protons of neighboringmolecules. Therefore, this type of substitution in this position isuseful for improving stability by preventing the uncoordinated nitrogenfrom being protonated. In addition, substituting a conjugating aryl ringat this position requires that the ring is fully twisted out of plane;therefore, aryl substitution at this site does not lower the tripletenergy of the complex. Therefore, the present invention is also based inpart on the discovery that the azaphenanthridine imidazole ligand may bea useful scaffold where a substituent on the ligand can be used tosterically block the potentially reactive site of the ligand withoutlowering the triplet energy.

Compounds of the Invention:

The compounds of the present invention may be synthesized usingtechniques well-known in the art of organic synthesis. The startingmaterials and intermediates required for the synthesis may be obtainedfrom commercial sources or synthesized according to methods known tothose skilled in the art.

In one aspect, the compound of the invention is a compound having theformula:

wherein A and B are independently selected from the group consisting ofa 5-membered or 6-membered carbocyclic or heterocyclic ring;

wherein one of A and B is an anionic coordinating atom, and the other ofA and B is a neutral coordinating atoms;

wherein X and Y are independently selected from the group consisting ofBR′, NR′, PR′, O, S, Se, C═O, S═O, SO₂, CR′R″, alkyl, aryl, SiR′R″, andGeR′R″;

wherein at least one of X and Y is present;

wherein M is Pt or Pd;

wherein R^(l) and R³ each independently represent mono, ordi-substitution, or no substitution;

wherein R² represent mono, di, tri, or tetra-substitution, or nosubstitution;

wherein R¹, R², R³, R′, and R″ are each independently selected from thegroup consisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any adjacent R¹, R², R³, R′, and R″ are optionally joined toform a ring.

In some embodiments, a substituent on the azaphenanthridine imidazoleligand can be used to sterically block the potentially reactive site ofthe ligand without lowering the triplet energy. In one embodiment, R4may be a bulky group, such as an aryl substituent, that inhibits closecontact of protons from the uncoordinated nitrogen:

In one embodiment, the compound has the formula:

wherein R is selected from the group consisting of hydrogen, deuterium,halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof.

In one embodiment, R is selected from the group consisting of alkyl,cycloalkyl, silyl, aryl, heteroaryl, and combinations thereof. Inanother embodiment, R is selected from the group consisting of methyl,ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 2-methylpropyl,pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl, 1,1-dimethylpropyl,1,2-dimethylpropyl, 2,2-dimethylpropyl, cyclopentyl, cyclohexyl, phenyl,2,6-dimethylphenyl, 2,4,6-trimethylphenyl, 2,6-diisopropylphenyl, andcombinations thereof.

In one embodiment, the compound is selected from the group consistingof:

wherein R⁶ represents mono, di, tri, or tetra-substitution, or nosubstitution;

wherein R⁴, R⁵, and R⁶ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof; and

wherein any adjacent R⁴, R⁵, and R⁶ are optionally joined to form aring.

A-B is not particularly limited, as long as A and B are independentlyselected from the group consisting of a 5-membered or 6-memberedcarbocyclic or heterocyclic ring, and one of A and B is an anioniccoordinating atom, and the other of A and B is a neutral coordinatingatoms. In some embodiments, A-B is the same ligand as theazaphenanthridine imidazole ligand. In other embodiments, A-B is adifferent ligand from the azaphenanthridine imidazole ligand. A-B may beconnected to the azaphenanthridine imidazole ring system through X, Y,or both to form a tetradentate ligand. Additionally, A-B may beoptionally substituted, and any adjacent substituents may be optionallyfused or joined to form a ring. X and Y are not particularly limited, aslong as they are capable of linking A-B to the azaphenanthridineimidazole ring system. In one embodiment, only one of X and Y ispresent. In one embodiment, X is present. In another embodiment, Y ispresent. In another embodiment, both X and Y are present.

In one embodiment, A-B is selected from the group consisting of:

wherein each X¹ to X¹³ are independently selected from the groupconsisting of carbon and nitrogen;

wherein X is selected from the group consisting of BR′, NR′, PR′, O, S,Se, C═O, S═O, SO₂, CR′R″, SiR′R″, and GeR′R″;

wherein R′ and R″ are optionally fused or joined to form a ring;

wherein each R_(a), R_(b), R_(c), and R_(d) may represent from monosubstitution to the possible maximum number of substitution, or nosubstitution;

wherein R_(L) represents mono substitution, or no substitution; whereinR_(a), R_(b), R_(c), R_(d) and R_(L) are each independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl,carbonyl, carboxylic acids, ester, nitrile, isonitrile, sulfanyl,sulfinyl, sulfonyl, phosphino, and combinations thereof;

wherein when R_(a), R_(b), R_(c), and R_(d) represent at least disubstitution, each of the two adjacent R_(a), two adjacent R_(b), twoadjacent R_(c), and two adjacent R_(d) are optionally fused or joined toform a ring;

wherein R_(L), is optionally a linker to function as X or Y; and

wherein when X¹ to X¹³ are used to link to X or Y, that X¹ to X¹³ iscarbon.

In one embodiment, the compound has the formula:

In one embodiment, the compound is selected from the group consistingof:

In some embodiments, the compound can be an emissive dopant. In someembodiments, the compound can produce emissions via phosphorescence,fluorescence, thermally activated delayed fluorescence, i.e., TADF (alsoreferred to as E-type delayed fluorescence), triplet-tripletannihilation, or combinations of these processes.

Devices:

According to another aspect of the present disclosure, a first device isalso provided. The first device includes a first organic light emittingdevice, that includes an anode, a cathode, and an organic layer disposedbetween the anode and the cathode. The organic layer may include a hostand a phosphorescent dopant. The emissive layer can include a compoundaccording to Formula I, and its variations as described herein.

The first device can be one or more of a consumer product, an electroniccomponent module, an organic light-emitting device and a lighting panel.The organic layer can be an emissive layer and the compound can be anemissive dopant in some embodiments, while the compound can be anon-emissive dopant in other embodiments. The organic layer can be acharge transporting layer and the compound can be a charge transportingmaterial in the organic layer in some embodiments. The organic layer canbe a blocking layer and the compound can be a blocking material in theorganic layer in some embodiments.

The organic layer can also include a host. In some embodiments, the hostcan include a metal complex. The host can be a triphenylene containingbenzo-fused thiophene or benzo-fused furan. Any substituent in the hostcan be an unfused substituent independently selected from the groupconsisting of C_(n)H_(n2+1), OC_(n)H_(2n+1), OAr₁, N(C_(n)H_(2n+1))₂,N(Ar₁)(Ar2), CH═CH—C_(n)H_(2n+1), C≡C—C_(n)H_(2n+1), Ar₁, Ar₁-Ar₂, andC_(n)H_(2n)-Ar₁, or no substitution. In the preceding substituents n canrange from 1 to 10; and Ar₁ and Ar₂ can be independently selected fromthe group consisting of benzene, biphenyl, naphthalene, triphenylene,carbazole, and heteroaromatic analogs thereof.

The host can be a compound comprising at least one chemical groupselected from the group consisting of triphenylene, carbazole,dibenzothiphene, dibenzofuran, dibenzoselenophene, azatriphenylene,azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene. The host can include a metal complex. The hostcan be a specific compound selected from the group consisting of:

and combinations thereof.

Formulations:

In yet another aspect of the present disclosure, a formulation thatcomprises a compound according to Formula I is described. Theformulation can include one or more components selected from the groupconsisting of a solvent, a host, a hole injection material, holetransport material, and an electron transport layer material, disclosedherein.

Combination With Other Materials

The materials described herein as useful for a particular layer in anorganic light emitting device may be used in combination with a widevariety of other materials present in the device. For example, emissivedopants disclosed herein may be used in conjunction with a wide varietyof hosts, transport layers, blocking layers, injection layers,electrodes and other layers that may be present. The materials describedor referred to below are non-limiting examples of materials that may beuseful in combination with the compounds disclosed herein, and one ofskill in the art can readily consult the literature to identify othermaterials that may be useful in combination.

HIL/HTL:

A hole injecting/transporting material to be used in the presentinvention is not particularly limited, and any compound may be used aslong as the compound is typically used as a hole injecting/transportingmaterial. Examples of the material include, but are not limited to: aphthalocyanine or porphyrin derivative; an aromatic amine derivative; anindolocarbazole derivative; a polymer containing fluorohydrocarbon; apolymer with conductivity dopants; a conducting polymer, such asPEDOT/PSS; a self-assembly monomer derived from compounds such asphosphonic acid and silane derivatives; a metal oxide derivative, suchas MoO_(x); a p-type semiconducting organic compound, such as1,4,5,8,9,12-Hexaazatriphenylenehexacarbonitrile; a metal complex, andcross-linkable compounds.

Examples of aromatic amine derivatives used in HIL or HTL include, butare not limited to the following general structures:

Each of Ar¹ to Ar⁹ is selected from the group consisting of aromatichydrocarbon cyclic compounds such as benzene, biphenyl, triphenyl,triphenylene, naphthalene, anthracene, phenalene, phenanthrene,fluorene, pyrene, chrysene, perylene, and azulene; the group consistingof aromatic heterocyclic compounds such as dibenzothiophene,dibenzofuran, dibenzoselenophene, furan, thiophene, benzofuran,benzothiophene, benzoselenophene, carbazole, indolocarbazole,pyridylindole, pyrrolodipyridine, pyrazole, imidazole, triazole,oxazole, thiazole, oxadiazole, oxatriazole, dioxazole, thiadiazole,pyridine, pyridazine, pyrimidine, pyrazine, triazine, oxazine,oxathiazine, oxadiazine, indole, benzimidazole, indazole, indoxazine,benzoxazole, benzisoxazole, benzothiazole, quinoline, isoquinoline,cinnoline, quinazoline, quinoxaline, naphthyridine, phthalazine,pteridine, xanthene, acridine, phenazine, phenothiazine, phenoxazine,benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each Ar isfurther substituted by a substituent selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof.

In one aspect, Ar¹ to Ar⁹ is independently selected from the groupconsisting of:

wherein k is an integer from 1 to 20; X¹⁰¹ to X¹⁰⁸ is C (including CH)or N; Z¹⁰¹ is NAr¹, O, or S; Ar¹ has the same group defined above.

Examples of metal complexes used in HIL or HTL include, but are notlimited to the following general formula:

wherein Met is a metal, which can have an atomic weight greater than 40;(y¹⁰¹-Y¹⁰²) is a bidentate ligand, Y¹⁰¹ and Y¹⁰² are independentlyselected from C, N, O, P, and S; L¹⁰¹ is an ancillary ligand; k′ is aninteger value from 1 to the maximum number of ligands that may beattached to the metal; and k′+k″ is the maximum number of ligands thatmay be attached to the metal.

In one aspect, (Y¹⁰¹-Y¹⁰²) is a 2-phenylpyridine derivative. In anotheraspect, (Y¹⁰¹-Y¹⁰²) is a carben ligand. In another aspect, Met isselected from Ir, Pt, Os, and Zn. In a further aspect, the metal complexhas a smallest oxidation potential in solution vs. Fc⁻/Fc couple lessthan about 0.6 V.

Host:

The light emitting layer of the organic EL device of the presentinvention preferably contains at least a metal complex as light emittingmaterial, and may contain a host material using the metal complex as adopant material. Examples of the host material are not particularlylimited, and any metal complexes or organic compounds may be used aslong as the triplet energy of the host is larger than that of thedopant. While the Table below categorizes host materials as preferredfor devices that emit various colors, any host material may be used withany dopant so long as the triplet criteria is satisfied.

Examples of metal complexes used as host are preferred to have thefollowing general formula:

wherein Met is a metal; (Y¹⁰³-Y¹⁰⁴) is a bidentate ligand, Y¹⁰³ and Y¹⁰⁴are independently selected from C, N, O, P, and S; L¹⁰¹ is an anotherligand; k′ is an integer value from 1 to the maximum number of ligandsthat may be attached to the metal; and k′+k″ is the maximum number ofligands that may be attached to the metal.

In one aspect, the metal complexes are:

wherein (O—N) is a bidentate ligand, having metal coordinated to atoms Oand N.

In another aspect, Met is selected from Ir and Pt. In a further aspect,(Y¹⁰³-Y¹⁰⁴) is a carbene ligand.

Examples of organic compounds used as host are selected from the groupconsisting of aromatic hydrocarbon cyclic compounds such as benzene,biphenyl, triphenyl, triphenylene, naphthalene, anthracene, phenalene,phenanthrene, fluorene, pyrene, chrysene, perylene, and azulene; thegroup consisting of aromatic heterocyclic compounds such asdibenzothiophene, dibenzofuran, dibenzoselenophene, furan, thiophene,benzofuran, benzothiophene, benzoselenophene, carbazole,indolocarbazole, pyridylindole, pyrrolodipyridine, pyrazole, imidazole,triazole, oxazole, thiazole, oxadiazole, oxatriazole, dioxazole,thiadiazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine,oxazine, oxathiazine, oxadiazine, indole, benzimidazole, indazole,indoxazine, benzoxazole, benzisoxazole, benzothiazole, quinoline,isoquinoline, cinnoline, quinazoline, quinoxaline, naphthyridine,phthalazine, pteridine, xanthene, acridine, phenazine, phenothiazine,phenoxazine, benzofuropyridine, furodipyridine, benzothienopyridine,thienodipyridine, benzoselenophenopyridine, and selenophenodipyridine;and the group consisting of 2 to 10 cyclic structural units which aregroups of the same type or different types selected from the aromatichydrocarbon cyclic group and the aromatic heterocyclic group and arebonded to each other directly or via at least one of oxygen atom,nitrogen atom, sulfur atom, silicon atom, phosphorus atom, boron atom,chain structural unit and the aliphatic cyclic group. Wherein each groupis further substituted by a substituent selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl,carboxylic acids, ester, nitrile, isonitrile, sulfanyl, sulfinyl,sulfonyl, phosphino, and combinations thereof.

In one aspect, the host compound contains at least one of the followinggroups in the molecule:

wherein R¹⁰¹ to R¹⁰⁷ is independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, acyl, carbonyl, carboxylicacids, ester, nitrile, isonitrile, sulfanyl, sulfinyl, sulfonyl,phosphino, and combinations thereof, when it is aryl or heteroaryl, ithas the similar definition as Ar's mentioned above. k is an integer from0 to 20 or 1 to 20; k′″ is an integer from 0 to 20. X¹⁰¹ to X¹⁰⁸ isselected from C (including CH) or N. Z¹⁰¹ and Z¹⁰² is selected fromNR¹⁰¹, O, or S.

HBL:

A hole blocking layer (HBL) may be used to reduce the number of holesand/or excitons that leave the emissive layer. The presence of such ablocking layer in a device may result in substantially higherefficiencies as compared to a similar device lacking a blocking layer.Also, a blocking layer may be used to confine emission to a desiredregion of an OLED.

In one aspect, the compound used in the HBL contains the same moleculeor the same functional groups used as the host described above.

In another aspect, the compound used in the HBL contains at least one ofthe following groups in the molecule:

wherein k is an integer from 1 to 20; L¹⁰¹ is an another ligand, k′ isan integer from 1 to 3.

ETL:

Electron transport layer (ETL) may include a material capable oftransporting electrons. Electron transport layer may be intrinsic(undoped), or doped. Doping may be used to enhance conductivity.Examples of the ETL material are not particularly limited, and any metalcomplexes or organic compounds may be used as long as they are typicallyused to transport electrons.

In one aspect, the compound used in ETL contains at least one of thefollowing groups in the molecule:

wherein R¹⁰¹ is selected from the group consisting of hydrogen,deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl, alkoxy,aryloxy, amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl,aryl, heteroaryl, acyl, carbonyl, carboxylic acids, ester, nitrile,isonitrile, sulfanyl, sulfinyl, sulfonyl, phosphino, and combinationsthereof, when it is aryl or heteroaryl, it has the similar definition asAr's mentioned above. Ar¹ to Ar³ has the similar definition as Ar'smentioned above. k is an integer from 1 to 20. X¹⁰¹ to X¹⁰⁸ is selectedfrom C (including CH) or N.

In another aspect, the metal complexes used in ETL contains, but is notlimited to, the following general formula:

wherein (O—N) or (N—N) is a bidentate ligand, having metal coordinatedto atoms O, N or N, N; L¹⁰¹ is another ligand; k′ is an integer valuefrom 1 to the maximum number of ligands that may be attached to themetal.

In any above-mentioned compounds used in each layer of the OLED device,the hydrogen atoms can be partially or fully deuterated. Thus, anyspecifically listed substituent, such as, without limitation, methyl,phenyl, pyridyl, etc. encompasses undeuterated, partially deuterated,and fully deuterated versions thereof. Similarly, classes ofsubstituents such as, without limitation, alkyl, aryl, cycloalkyl,heteroaryl, etc. also encompass undeuterated, partially deuterated, andfully deuterated versions thereof.

In addition to and/or in combination with the materials disclosedherein, many hole injection materials, hole transporting materials, hostmaterials, dopant materials, exiton/hole blocking layer materials,electron transporting and electron injecting materials may be used in anOLED. Non-limiting examples of the materials that may be used in an OLEDin combination with materials disclosed herein are listed in Table Abelow. Table A lists non-limiting classes of materials, non-limitingexamples of compounds for each class, and references that disclose thematerials.

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Experimental

In Formula I, azaphenanthridine imidazole is linked through theimidazole or pyridyl ring through X or Y or both to form a tetradentateligand coordinated to M. Preferably, M ═Pt, Pd. The ligand precursorsand the inventive metal complexes of the general Formula I may beprepared by processes known to those skilled in the art. Suitableprocesses are mentioned, for example, in WO2012116231, which isincorporated by reference herein in its entirety, and the literaturecited therein for general tetradentate Pt complexation. The inventivemetal complexes can be purified by processes known to those skilled inthe art. Typically, the workup and purification are affected byextraction, column chromatography, recrystallization, and/or sublimationby processes known to those skilled in the art.

An exemplary process for preparing the inventive metal complexescontaining a ligand according to Formula I is detailed below by using asynthetic path shown below:

The benzyl or 4-methoxybenzyl protected hydroxynicotinonitrile can beprepared according to the method of Baldwin et al. (U.S. Pat. No.4,374,140, which is incorporated by reference herein in its entirety).Reaction of this with the boronic ester and a palladium catalyst wouldgive the azaphenanthridine. The preparation of the tribromoaldehyde isgiven in Tsai et al. (U.S. Patent Application No. 20100148663, which isincorporated by reference herein in its entirety). Reaction of thealdehyde with phenanthridine in isopropanol would give theazaimidazophenanthridine. Reaction of this with isopropenylboronic acidpinacol ester would give the isopropenyl substituted intermediate.Hydrogenation of this would simultaneously reduce the olefins and removethe benzyl or 4-methoxybenzyl group. The phenol can be treated withtriflic anhydride and triethylamine to give the triflate. The triflatecan be converted to the iodide using the methodology of Thompson et al.(Synthesis (4) pp 547-550 (2005), which is incorporated by referenceherein in its entirety). The iodide can be coupled with the phenol usingthe method of Altman et al. (Organic Letters 9 (4) pp 643-646 (2007),which is incorporated by reference herein in its entirety). Metallationwith a Platinum source such as K₂PtCl₄ in acetic acid would afford thefinal complex.

Several comparative examples are provided.

Comparative example 1 is a bis-bidentate imidazole phenanthridineplatinum complex. It is nonemissive in room temperature solution andonly weakly emissive in the solid state. The 77K emission spectrum forComparative Example 1 is provided in FIG. 3. The highest energy peakemission is 472 nm.

The emissive properties of Comparative Example 1 are compared directlyto Comparative Example 2. Comparative Example 2 is a symmetrictetradentate imidazole phenanthridine platinum complex where theimidazole phenanthridines are bridged by oxygen to provide onetetradentate ligand.

In comparison to Comparative Example 1, Comparative Example 2 isbrightly emissive in room temperature solution and has a very high PLQYdoped in PMMA matrix of 84%.

The emission spectra in solid state PMMA matrix, and 77K and roomtemperature 2-methyl tetrahydrofuran (THF) solvent are shown in FIG. 4.The highest energy peak emission in solid state PMMA matrix is 480 nm.

One drawback for both Comparative Examples 1 and 2 is that the emissionenergy is not blue enough for display and lighting applications. Theresults described herein demonstrate that substituting nitrogen in thering system provides a strong blue-shifting effect not observed incompounds such as Comparative Examples 1 and 2, where there is noadditional nitrogen in the ring system.

Density functional theory (DFT) calculations are shown in Table 1. DFTcalculations were performed using the B3LYP/cep-31g/THF functional,basis set and solvent polarization, respectively.

The blue-shifting effect of the uncoordinated nitrogen is clearly shownin density functional theory (DFT) calculations by comparing the tripletenergies of invention Compounds 1-3 to Comparative Example 2. As shownin Table 1, Compounds 1-3 have calculated triplet energies in the rangeof 480 nm, while the triplet energy of Comparative Example 2 iscalculated to be 497 nm.

In order to calibrate calculated values to experimental results, theexperimentally determined triplet energy of Comparative Example 2 is 480nm, as shown in FIG. 4. Furthermore, DFT and experimental results for ablue-shifted asymmetric derivative, Comparative Example 3, are shown inTable 1 and FIG. 5. Comparative Example 3 is calculated by DFT to have atriplet of 479 nm. In room temperature and 77K 2-methyl tetrahydrofuransolvent, the triplet is experimentally determined to be 456 and 451 nm,respectively. In one embodiment, the invention compounds described hereare in a desirable blue emission range of 450-470 nm. Another advantagefor the compounds of the invention are that they can be designed assymmetric structures, unlike the blue emissive Comparative Example 3.This can be beneficial for synthetic and stability reasons.

It can be seen in space filling models of Compound 2, calculated bydensity functional theory (DFT), that an aryl substituent stericallyshields the uncoordinated nitrogen from close contact of a neighboringintra or intermolecular proton atom. This site blocking substituent maybe a desirable feature for improving the stability. Furthermore, as thearyl substitution at this site necessarily twists out of the plane ofthe ligand, there is a minimal effect on the triplet energy of thecomplex. It is shown in Table 1 that the calculated triplet for an arylsubstituted compound, Compound 2, is nearly identical to the methylsubstituted analogue, Compound 1.

The calculated and experimental data for Comparative Example 5, aniridium analogue with an azaphenanthridine imidazole ligand, is alsoshown for comparison to the tetradentate platinum complex. DFTcalculations for Comparative Example 5, the meridional (mer) isomer oftris iridium imidazole aza-phenanthridine complexes, predict a tripletenergy of 448 nm. Furthermore, the experimental 77K solution emissionspectrum is shown in FIG. 6. The highest energy peak emission forComparative Example 5 is 431 nm. Comparative Example 5 is nonemissive inroom temperature solution. Therefore, while Comparative Example 5 hasdeep blue emission, it is actually too high in energy to be supported byconventional host materials that typically contain carbazole,dibenzofuran and dibenzothiophene moieties, due to triplet quenching.Based on the predicted triplet energy, the tetradentate platinum systemis not expected to suffer from this limitation, and is expected to emitwith high photoluminescent efficiency comnared to a bidentate analogue.

TABLE 1 Density functional theory (DFT) calculations HOMO LUMO GapDipole S1_(THF) T1_(THF) Structure (eV) (ev) (ev) (Debye) (nm) (nm)Compound 1

−5.74 −1.94 −3.80 9.19 402 481 Compound 2

−5.75 −1.95 −3.79 10.23 403 482 Compound 3

−5.75 −1.95 −3.80 11.42 403 481 Comparative Example 2

−5.28 −1.60 −3.67 6.70 420 497 Comparative Example 3

−5.28 −1.65 −3.62 10.19 418 479 Comparative Example 4

−5.56 −1.52 −4.04 10.35 411 447 Comparative Example 5

−5.57 −1.50 −4.08 6.03 390 448

It is understood that the various embodiments described herein are byway of example only, and are not intended to limit the scope of theinvention. For example, many of the materials and structures describedherein may be substituted with other materials and structures withoutdeviating from the spirit of the invention. The present invention asclaimed may therefore include variations from the particular examplesand preferred embodiments described herein, as will be apparent to oneof skill in the art. It is understood that various theories as to whythe invention works are not intended to be limiting.

The disclosures of each and every patent, patent application, andpublication cited herein are hereby incorporated herein by reference intheir entirety. While this invention has been disclosed with referenceto specific embodiments, it is apparent that other embodiments andvariations of this invention may be devised by others skilled in the artwithout departing from the true spirit and scope of the invention. Theappended claims are intended to be construed to include all suchembodiments and equivalent variations.

1.-20. (canceled)
 21. A compound of

wherein A and B are independently selected from the group consisting ofa 5-membered or 6-membered carbocyclic or heterocyclic ring; and one ofA and B is an anionic coordinating atom, and the other of A and B is aneutral coordinating atom; at least one of linking groups X and Y ispresent, wherein X and Y are independently selected from the groupconsisting of BR′, NR′, PR′, O, S, Se, CR′R″, alkylene, phenyl, SiR′R″,and GeR′R″; M is Pt or Pd; R is selected from the group consisting ofhydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl, arylalkyl,amino, silyl, alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl,heteroaryl, nitrile, and isonitrile; R¹ and R³ each independentlyrepresent mono, or di-substitution, or no substitution; R² representmono, di, tri, or tetra-substitution, or no substitution; wherein R¹,R², R³, R′, and R″ are each independently selected from the groupconsisting of hydrogen, deuterium, halide, alkyl, cycloalkyl,heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl,cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl, nitrile, andisonitrile; or any two adjacent R¹, R², R³, R′, and R″ are optionallyjoined to form a ring.
 22. The compound of claim 21, wherein M is Pt.23. The compound of claim 21, wherein R is selected from the groupconsisting of alkyl, cycloalkyl, silyl, aryl, and heteroaryl.
 24. Thecompound of claim 21, wherein R is selected from the group consisting ofmethyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl,2-methylpropyl, pentyl, 1-methylbutyl, 2-methylbutyl, 3-methylbutyl,1,1-dimethylpropyl, 1,2-dimethylpropyl, 2,2-dimethylpropyl, cyclopentyl,cyclohexyl, phenyl, 2,6-dimethylphenyl, 2,4,6-trimethylphenyl, and2,6-diisopropylphenyl.
 25. The compound of claim 21, wherein X absent.26. The compound of claim 21, wherein Y is absent.
 27. The compound ofclaim 25, wherein the compound is selected from the group consisting of:

wherein R⁶ represents mono, di, tri-substitution, or no substitution;R⁴, R⁵, and R⁶ are each independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, nitrile, and isonitrile; orany two adjacent R⁴, R⁵, and R⁶ are optionally joined to form a ring.28. The compound of claim 26, wherein the compound is selected from thegroup consisting of:

wherein R⁶ represents mono, di, tri-substitution, or no substitution;R⁴, R⁵, and R⁶ are each independently selected from the group consistingof hydrogen, deuterium, halide, alkyl, cycloalkyl, heteroalkyl,arylalkyl, alkoxy, aryloxy, amino, silyl, alkenyl, cycloalkenyl,heteroalkenyl, alkynyl, aryl, heteroaryl, nitrile, and isonitrile; orany two adjacent R⁴, R⁵, and R⁶ are optionally joined to form a ring.29. The compound of claim 21, wherein A-B is selected from the groupconsisting of:

wherein each X¹ to X¹³ are independently selected from the groupconsisting of carbon and nitrogen; and if carbon then R_(a), R_(b),R_(c), and R_(d) independently represent from mono substitution to thepossible maximum number of substitution, or no substitution X isselected from the group consisting of NR′, O, S, Se, C═O, CR′R″, SiR′R″,and GeR′R″; R_(L) represents mono substitution, or no substitution;R_(a), R_(b), R_(c), R_(d) and R_(L) are each independently selectedfrom the group consisting of hydrogen, deuterium, halide, alkyl,cycloalkyl, heteroalkyl, arylalkyl, alkoxy, aryloxy, amino, silyl,alkenyl, cycloalkenyl, heteroalkenyl, alkynyl, aryl, heteroaryl,nitrile, and isonitrile; or independently R_(a), R_(b), R_(c), and R_(d)represent at least di substitution, and two adjacent R_(a), two adjacentR_(b), two adjacent R_(c), and two adjacent R_(d), join to form a ring;and optional linking group X or Y joins with A-B through R^(L) or anyone X¹ to X¹³ indicated by the dotted lines.
 30. The compound of claim21, wherein the compound is selected from the group consisting of:


31. An organic light emitting device comprising: an anode; a cathode;and an organic layer disposed between the anode and the cathode, theorganic layer comprising a compound of claim
 21. 32. The device of claim31 selected from the group consisting of a consumer product, anelectronic component module, and a lighting panel.
 33. The device ofclaim 31, wherein the organic layer further comprises a host; whereinthe host comprises a triphenylene containing benzo-fused thiophene orbenzo-fused furan; wherein any substituent in the host is an unfusedsubstituent independently selected from the group consisting ofC_(n)H_(n2+1), OC_(n)H_(n2+1), OAr₁, N(C_(n)H_(2n+1))_(2,) N(Ar₁)(Ar₂),CH═CH—C_(n)H_(2n+1), C≡CC_(n)H_(2n+1), Ar₁, Ar₁-Ar₂, C_(n)H2n-Ar₁, or nosubstitution; wherein n is from 1 to 10; and wherein Ar₁ and Ar₂ areindependently selected from the group consisting of benzene, biphenyl,naphthalene, triphenylene, carbazole, and heteroaromatic analogsthereof.
 34. The device of claim 31, wherein the organic layer furthercomprises a host, wherein the host comprises at least one chemical groupselected from the group consisting of triphenylene, carbazole,dibenzothiphene, dibenzofuran, dibenzoselenophene, azatriphenylene,azacarbazole, aza-dibenzothiophene, aza-dibenzofuran, andaza-dibenzoselenophene.
 35. The device of claim 31, wherein the organiclayer further comprises a host and the host is selected from the groupconsisting of:

and any one mixture thereof.
 36. A formulation comprising the compoundof claim 21.